Conventionally, as the exterior construction material used for covering an existing wall surface, various kinds of fired tiles, various kinds of natural stones, engineered stones and the like (hereinafter, referred to as “material” or “module tile” depending on a situation) have been generally used. As the tile material as construction material, as shown in FIG. 9, square JIS standard tile materials 7–13 mm in thickness and 300 mm long square or 600 mm long square, and processed materials of various shapes such as long-size tiles and small-size tiles have been marketed and the surface of the tile is subjected to coating with glaze and the porcelain tile and the natural and engineered stone is polished. When using as for example, the wall materials on construction site, generally, a method of bonding its rear surface 73 to the wall surface while butting its edge to an existing wall surface so as to secure a predetermined area has been used. However, when treating a right angle wall surface, that is, a corner portion 91 of the existing wall surface by butting two tile sheets, if the butting angle, more specifically, an inclination angle of 45° and an inclined face (slope) are not formed accurately, there occurs a large deflection in the butting face, so that no straight wall surface can be obtained, thereby possibly inducing critical damage to the quality of finished surface (see FIG. 8).
Although the exterior construction material represented by the tile material has attracted public popularity in terms of its finished luxurious appearance and excellent heat insulation effect, it has been widely prevalent as an exterior construction material for the wall surface. However, because its base material is a specific hard brittle material, originally, its processibility is very poor and various cares have been paid to even straight cutting work. As a disc like diamond cutter for cutting, for example, a porcelain tile, a so-called rim type diamond saw blade in which diamond abrasive portions 3 mm in thickness are provided continuously on the outer peripheral face of a relatively large substrate has been proposed, the diamond saw blade being capable of cutting without scattering of tile glaze or chipping by providing right and left edge portions of the grinding stone portion alternately with a cut-out groove having a width ½ the thickness of the grinding stone portion in proportion to the thickness of the grinding stone portion (see, for example, Japanese Patent Application Laid-Open No. 2001-300855). Further, as the disc like diamond cutter for cutting the porcelain tile, there has been proposed a cutter in which the stiffness of its substrate is intensified by forming the substrate on an outer portion slightly thinner than the diamond abrasive chip layer formed on the outer peripheral face of the substrate while forming a substrate portion in the center of the substrate thicker than the outer portion of the substrate, so as to prevent deformation of the substrate, thereby blocking hand movement originating therefrom to realize precision cutting of the porcelain tile (see for example, Japanese Patent Application Laid-Open No. 2002-205274). A number of proposals have been made and realized for practical application.
Although the processing of the tile material require the above-described care for even cutting along a simple straight line, the side face processing of executing exterior construction by abutting two tile materials on a right angle corner of the existing wall from both sides requires extremely high skill. Thus, conventionally, this work depends upon the skilled engineer specialized in such a edge processing or a tile material in which an inclination angle of 45° is formed on the edge of a tile material is manufactured by means of a special machine for the edge processing developed by a edge processing manufacturer (tile bonding processing manufacturer) or the corner piece material 91 shown in FIG. 10 is manufactured and sold to a construction worker as special product. In FIG. 10, reference numeral 92 denotes a tile material.
However, it cannot be denied that such construction work in this industry includes makeshift factors and it is more difficult than expected to purchase the tile materials whose edges are processed to 45° or the corner piece materials 91 in a sufficient quantity in order to apply them to actual construction. Further, because it is necessary to depend on the processing of subcontractor by, for example, booking him for the processing, a large burden is induced in a serious price competition and there are unstable factors from viewpoints of due date. Thus, although a method of carrying out exterior construction by the means shown in FIG. 11 has been tried, in this case, the wall surface is coated and/or polished in conditions in which a edge 932 not treated of the tile material 93 is exposed outside and because this provides a strange contrast with the tile material surface 931 subjected to coating with glaze or polishing, a further special processing is required for correcting it so that not only the finished face quality drops but also the processing cost can be raised largely.
Although any grinding tool having a function for blocking hand movement has been proposed and a tile material and corner piece material 91 whose edge is preliminarily processed to 45° have been manufactured and marketed and further, it has been confirmed that specialized processing subcontractors exist, it is more difficult than expected to estimate the tile materials and corner piece materials 91 for use accurately and purchase, and complete a construction using them without any insufficiency. Often those components are purchased more than a necessary amount thereby leading to increase in cost or the necessity of making additional order occurs during construction leading to a cause for delay of the due date. Further, making orders to such specialized subcontractor itself becomes an excessive burden, and therefore, this is an important problem which is desired to be solved soon.
Accordingly, in views of the current situation of exterior wall construction with such tile materials and the like, an object of the present invention is to provide a grinding tool which is capable of starting processing work immediately on construction site and requires no special skill, thereby enabling grinding of the edge processing easily and accurately with a specified angle, more specifically, an angle of 45° just by simple manual work by average-skilled workers.